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Gastrointestinal Polyps

Gastrointestinal polyps are being identified more frequently today because of increased awareness, screening and improved diagnostic tools. The entire gastrointestinal tract is at risk for polyp development but the adult colon and rectum account for the majority of polyps.

  • Colorectal cancer is the fourth most common form of cancer in the US and has the second highest cancer mortality
  • In 2002, 148,000 new cases of colorectal cancer were anticipated with more than 56,000 deaths
  • There is a 6% life time risk of colorectal cancer. The incidence is higher in men, especially African American. Only about 35% of cases are diagnosed at an early stage
  • The transition from benign (noncancerous) adenoma to carcinoma (cancerous polyp) has been established. A series of genetic mutations involving several genes is necessary for malignant transformation over an extended period (probably years with 95% of colorectal malignancies arising from adenomas)
  • Gastrointestinal (GI) malignancy is unusual in childhood

Though any part of the GI tract may develop a polyp, the emphasis here is on colon polyps

Anatomy and Physiology

  • The large bowel absorbs 90% of the water content of the digested food it receives from the small intestine. It also propels the residue towards the rectum, where it is stored and expelled with a bowel movement
  • The colon is divided into four segments and two flexures (Figure 1):
    1. Cecum is the first portion of the large bowel and is joined to the small bowel. The appendix lies at the lowest portion of the cecum (See Appendectomy)
    2. Ascending colon extends upwards from the cecum to the hepatic flexure near the liver
    3. Transverse colon extends across the upper abdomen to the splenic flexure
    4. Descending colon extends from the splenic flexure downwards to the start of the pelvis
    5. Sigmoid colon extends from the descending colon to the rectum
  • The wall of the colon is composed of four layers (Figure 2):
    1. Mucosa - The epithelial (single layer of cells) lining is flat and regenerates itself every 3-8 days. Small glands lie beneath the surface.
    2. Submucosa - The area between the mucosa and circular muscle layer and is separated from the mucosa by a thin layer of muscle, the muscularis mucosa
    3. Muscularis propria - The inner circular and outer longitudinal muscle layers
    4. Serosa - The outer single cell thick covering of the bowel. Similar to the peritoneum, the layer of cells that lines the abdomen
  • The colon does not have lymphatic channels in the submucosa between the mucosa and muscle. This is important because tumors invading into this area do not have lymphatic channels through which to metastasize (spread)
Figure 1 - Anatomy of the colon.
Figure 2 - Cross-section through the wall of the colon (see text). © C. Hogan


Pathology

  • Intestinal polyps arise from the lining epithelium and protrude into the bowel lumen. Intestinal polyps are typically pedunculated (having a stalk) (Figure 3) or sessile (flat broad base) (Figure 4)
Figure 3 - Example of a pedunculated polyp. © C. Hogan
Figure 4 - Example of a sessile polyp.© C. Hogan

Sessile polyps have a higher malignancy rate than pedunculated polyps

  • Increasing adenoma size is associated with increasing cancer risk:
    1. 2% risk for 0.6 cm (centimeter) to 1.5 cm adenomatous polyp
    2. 20% risk for 1.6 cm to 2.5 cm
    3. 40% risk for 2.6 cm to 3.5 cm
    4. 75% risk for >3.5 cm
  • Adenomatous polyps (benign) are present in three epithelial architectural patterns:
    1. Tubular adenoma is composed of more than 75% tubular (normal appearing) glands. It is the most common form with 90% of tubular adenomas found in the colon
    2. Villous adenoma is composed of greater than 50% villous (surface projections) architecture. Villous architecture is seen in the small bowel
    3. Tubulovillous adenoma contains 25-50% villous architecture
  • Pedunculated polyps have beenclassification according to the depth of tumor invasion (by Haggitt)
    1. Level 0 - carcinoma in situ or intramucosal and not invasive (doesn't penetrate the basement membrane)
    2. Level 1 - carcinoma invading through the muscularis mucosa into the submucosa but limited to the head of the polyp
    3. Level 2 - carcinoma invading the level of the neck of the polyp
    4. Level 3 - carcinoma invading any part of the stalk
    5. Level 4 - carcinoma invading into the submucosa of the bowel wall below the stalk of the polyp but above the muscularis propria
  • All sessile polyps with invasive carcinoma are in pedunculated polyp level 4. Submucosal invasion of a sessile polyp can be classified into three levels (by Kudo):
    1. Sm 1 - invasion into the upper third of the submucosa
    2. Sm 2 - invasion into the middle third of the submucosa
    3. Sm 3 - invasion into the lower third of the submucosa
  • Juvenile polyp of the colon is the most common polyp of childhood. It has no associated genetic defect and is an overgrowth of normal epithelium with a mild inflammatory reaction. It does not predispose to malignancy.
  • Juvenile polyposis is a rare genetic condition characterized by multiple polyps. Polyps frequently number from 50 to 100 and have a tendency to develop into malignancies
  • Familial Adenomatous polyposis is the most common genetic polyposis syndrome. Hundreds or thousands of polyps ultimately appear in the colon and rectum and frequently become malignant within 10 years. These tumors require resection of the entire colon and rectum
  • There are several syndromes that have a slightly increased incidence of late bowel malignancy:
    1. Peutz-Jeghers Syndrome is an inherited abnormality in a gene on chromosome 19, which seems to result in a tendency toward benign and cancerous tumors most commonly seen with small bowel polyps. The most distinctive feature is freckles that occur on the lips, mouth, around the eyes, nose, anus, hands and feet. The freckles usually occur in infancy or childhood and may fade with age.
    2. Cowden Syndrome is an inherited disease that causes hamartomatous neoplasms of the skin, thyroid gland, gastrointestinal tract, bones, brain, spinal cord, eyes, and genitourinary tract. The skin is involved in 90-100% of cases and the thyroid 65% of cases
    3. Turcot's Syndrome involves the association of a primary malignant brain tumor and multiple colon and rectal adenomas. These patients are at risk for basal cell cancers of the scalp as well as stomach cancer
    4. Gardner's Syndrome involves the presence of large numbers of polyps in the bowel. These patients are at risk for bone and soft tissue cancers

History and Physical

  • A family history is particularly important with children where multiple polyps are concerned
  • Polyps usually present with rectal bleeding
  • Rectal examination is often normal but a polyp may be felt on rectal exam

Tests

  • A number of different flexible fiber optic scopes are available to examine most of the gastrointestinal tract (Figure 5)
  • These scopes allow direct visualization and biopsy or removal of the intestinal polyps
  • Most endoscopes project onto a video screen
  • Complete colon examination is important because a synchronous (second coexisting polyp) adenoma will be present in 40% of adenoma cases. A synchronous cancer will exist in 2-5% of colorectal cancers.
  • Experienced endoscopists will be able to do complete colonoscopy in greater than 91% of cases
    1. Anoscopic exam - a short metal instrument, 12-15 cm long is inserted into the rectum for direct visualization
    2. Sigmidoscopy - a 25 cm. rigid scope is advanced through the rectum to the sigmoid colon
    3. Flexible sigmoidoscopy - a flexible fiberoptic scope is advanced through the rectum to 60 cm
    4. Colonoscopy - a flexible fiber optic scope is advanced through the rectum to examine the entire colon (See Colonoscopy)
    5. Various flexible scopes are available to examine the esophagus, stomach, duodenum and part of the small bowel for mucosal polyps
  • Barium enema - a Barium containing contrast is introduced peer rectum to fill the entire colon, this study may be done with air contrast
  • UGI and Small Bowel Barium contrast studies are available
  • Virtual Colonoscopy - this is a newer technique where after bowel cleansing air is introduced into the colon a CAT scan of the colon is performed, a major short coming is inability to perform biopsy or polyp removal (Figure 6)
Figure 5 - The various endoscopes that are used for examination of the colon and the extent of bowel viewed by the endoscope.
Figure 6 - CT virtual colonoscopy.

Indications

  • Tissue diagnosis to determine whether benign or malignant
  • Remove to prevent malignant transformation
  • Remove to prevent ongoing bleeding
  • Remove to prevent bowel obstruction or intussusception (See Intussusception)

Surgery

  • Most esophageal, gastric, duodenal and colorectal polyps will be evaluated by endoscopy with the goal of removal or biopsy. Benign polyps should be removed in their entirety and submitted for complete microscopic examination. If malignancy is suspected or obvious, biopsy only may be indicated with subsequent bowel resection (See Colectomy)
  • Pedunculated polyps will usually be removed by snaring them with an electrocautery loop (Figure 7). The head, neck, and stalk is removed down to the base of the polyp. They are usually removed intact and can be studied precisely with the microscope
Figure 7 - Polyp in electrocautery loop snare. © C. Hogan
  • Sessile polyps are more difficult to remove because of their flat broad bases. Often they are removed in piece meal fashion that makes the microscopic evaluation more difficult
    1. A newer technique known as Endoscopic Mucosal Resection (EMR) is gaining support where sessile polyps are concerned
    2. EMR is indicated in non-pedunculated polyps that cannot be removed by standard snare techniques
    3. With this technique a suction cap with or without saline injected under the polyp is employed in an effort to create a pedicle. If a pedicle can be created with saline and suction, the polyp can be snared
    4. The sessile lesion may just require saline injection underneath it to create an elevated lesion that can be snared without suction cap
    5. This technique allows more precise microscopic examination with initial evaluations showing an upgrading (more disease identified) because of the polyp being removed intact
  • Methods to control bleeding during endoscopic polyp removal are:
    1. Thermal (heating) methods
      • Bipolar electrocautery - heats between two adjacent points
      • Monopolar electrocautery - heats at tip of electrode (Figure 8A, B)
      • Heater probe
      • Argon Plasma Coagulation
      • Microwave
      • Laser
    2. Injection
      • Epinephrine - acts to constrict the vessels
      • Alcohol
      • Ethanolamine - constricts vessels
      • Cyanoacrylate - surface glue
      • Thrombin - aids clotting
      • Fibrin - aids clotting
    3. Mechanical
      • Hemoclips - small metal clips
      • Sewing
      • Band ligation
      • Endoloop
    4. Combinations of the above may be utilized.
  • Additional decision making is determined by the microscopic report
Figure 8a - Sessile polyp. Courtesy M. Takriti, MD
Figure 8b - Cauterized base of polyp after removal, Courtesy M. Takriti, MD

Complications

  • Perforation or tear through the bowel wall that may require surgery
  • Bleeding may occur from the site of biopsy or polypectomy. It is usually minor and stops on its own or can be controlled through the colonoscope. Rarely blood transfusions or surgery may be required
  • Other potential risks include:
    1. Reaction to the sedatives
    2. Complication from associated heart or lung disease
    3. Localized irritation of the vein where medication was injected. Applying hot packs or hot moist towels may relieve discomfort
  • Although complications after colonoscopy are uncommon, it is important for the patient to recognize early signs of any possible complication. The patient should contact the physician if any of the following symptoms are being observed:
    1. Severe abdominal pain
    2. Fever or chills
    3. Rectal bleeding of more than one-half cup. Bleeding can occur several days after polyp removal

After Care

  • After the test, patients are monitored in the recovery area for 30 - 45 minutes, until the effects of sedation have worn off. They will need to make arrangements for somebody to drive them home (not a taxi) and to stay with them for the remainder of the day because the sedation affects judgment and reflexes for the rest of the day. No driving or working is allowed until the next day. It is advised to have somebody stay with the patient for the rest of the day
  • There may be some cramping or bloating because of the air introduced into the colon during the examination. This disappears with the passage of flatus (gas)
  • Generally the patient should be able to eat after the endoscopy, but the physician may restrict the diet or activities, especially, after extensive endoscopic work (i.e. large polypectomy, control of bleeding, etc).
  • The doctor will discuss with the patient or designated companion any further instructions or need for follow up